Figure 2. Iterative oxidation/reduction cycles of p58C on a single electrode surface.

A) The scheme depicts the redox switch in p58C DNA binding. When oxidized, p58C is bound tightly to DNA. Reduction converts p58C to a weakly DNA-associated state. B) Cyclic voltammetry following five sequential oxidation reactions on one DNA-modified electrode of a multiplex chip. Electrolysis conditions (E_applied = 412mV vs. NHE) are identical for each oxidation. A cathodic peak at ⁻130- ⁻140mV vs. NHE is regenerated each time in the first CV scan after oxidation. The cathodic peak corresponds to a reduction of tightly bound, oxidized p58C, to weakly associated p58C. Charge transfer values in the cathodic peaks for scans 1–5, in chronological order, are 65.4 nC, 112.4 nC, 116.4 nC, 151.1 nC, and 170.9 nC. Peak charge increases over trials due to increasing p58C at the solution/DNA interface. Electrochemistry was performed on 16 µM p58C in 20 mM Tris, pH 7.2, 75 mM NaCl, 100 mV/s scan rate for CV, using a Ag/AgCl reference electrode.